Limit switch



L. P. HUTT LIMIT SWITCH Aug. 26, 1930.

Filed Jan. 18, 1928 Milf Inverxl'or L eonclrcl P. HLLTT, b5

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Patented Aug. r26, 1930A UNITED STATES PATENT OFFICE LEONARD P. BUTT, OFSCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, ACORPORATION 0F NEW YORK LIMIT SWITCH Application led January 18, 1928.

The present invention relates to limit switches and has for its objectthe provision of an improved form of limit switch mechanism that has awide range of adjustment and will open its contacts accurately after adesired number of revolutions of an operating member has occurred.Moreover, the improved form of limit switch of the present invention isof compact construction, permitting the switch to be utilized wherespace requirements are at a premium. In addition, the adjustment ot theswitch to open its contacts after the desired number of revolutions hasoccurred may be readily eftected by hand without the use of tools or theloosening of any screws or other fastenings.

lhe improved limit switch preferably is provided with two circuitcontrolling members, one for each direction of operation so as to have awide field of application, although it is particularly adapted for usein window control service or the like. In such service the windowsordinarily are opened and closed by means of an electric motor and thelimit switch is employed to automatically interrupt the energizingcircuit Ot' the motor when the window is opened and also when the windowis closed. A high degree of accuracy in the control of the operatingmotor is required to effect a proper closing of the window. Thus if thelimit switch interrupts the motor circuit too soon the window willremain slightly ajar while if the limit switch opens the motor circuitafter the window is fully closed the motor stalls and remains energized.Consequently, a very precise actuation of the limit switch just as thewindow reaches the full closed position is required. A lesser degree oaccuracy of operation of the limit switch is required in opening thewindow since the degree of opening of the window ordinarily is not ofgreat importance.

In the accompanying drawing Fig. 1 is a side view of the improved formof limit switch embodying the present invention and Fig. 2 is an endview with certain of the operating parts in section in order more fullyto reveal the details of construction.

As shown in the drawing the limit switch Serial No. 247,701.

mechanism is mounted within and totally enclosed by the enclosing casinglO, which, is provided with the removable side covers 11. The operatingsha-tt 12 :tor the limit switch is rotatably supported in the bearing 13which preferably is cast integrally with the casing 10, as indicated inFig. 1. The shaft 12 is arranged to be rotated in accordance with theoperation of the device to be controlled as for exampie the windowoperating mechanism and carries the worm gear 14 which meshes with thegear wheel 15. As more clearly shown in Fig. 2, the gear wheel 15rotates upon the shaft 1G which is iXedly secured to the pedestalsupport 17 extending from the casing 10. The gear wheel 15 carries twocam members 18 and 19 which operate respectively the movable contactmembers 2O and of the limit switch mechanism.

The switch operating cam element 18 is mounted upon the gear wheel 15 sothat it may be easily adjusted to any one of a plurality ot angularpositions with respect to the gear wheel. This is accomplished, byproviding the gear wheel. 15 with a series of locking holes into whichthe locking pins 23 carried by the cam member 18 may be inserted. Thecam member 18 is pressed by the spring 24; against the side ot the gearwheel 15 to maintain the locking pins 23 irmly in engagement with theholes 22. The spring 24 is maintained under compression by the washer 25which is held on the hub 15 of the .vheel 15 by the ring 2b, which isarranged to snap into. a groove Jrormed in the hub 15.

TVith the mounting of the cam member just described, the cam member maybe readily adjusted in the following manner: By moving the cam member 18aXiallyto the left along the hub 15 against the strain of the spring 24,the pins 23 are disengaged 'trom the locking holes 22. The cam member 18then can be rotated to any desired angular position upon the gear wheel15 in which the two locking pins 23 register with any selected pair ofthe holes 22. Upon the release of the cam member 18 the pins 23 reengagewith the selected locking holes and firmly maintain the cam member 18 inthe selected angular position upon the gear wheel 15 so as to rotate asa unit therewith. It will be observed that the gear wheel 15 is heldagainstaxial movement on its shaft 16 by means ot the screw 27 which isthreaded into the end ot the shaft 1G and holds the washer 2S againstthe end tace ot the hub 15. For convenience in adjusting the angularposition oi' the operating` cam 18, the cam is provided with a serra tedperiphery such as shown in Fig. 1. This permits the cam to be readilygrasped, retracted out of engagement. with the gear wheel 15, androtated to the desired angular position on the gear wheel 15 without theuse tools.

'lfhe cani member 19 is 'ixedly secured to the gear wheel 15 b v thescrews 29. ln order 'to adjust the operating,` position ot the cammember 19 with respect to the operating shaft 12, itis only necessarjg.to remove the screw 2.7 and the washer 28. lhis permits the (gear wheel15 and the cam members mounted thereon to be moved l unit axially along'the .shaft 16 so as to diseigas c the worm wheel 111. rhereupon the`gear wheel 15 may be rotated '5o bring the cam member 1.() into thedesired oj erating position when the gear 15 is roene'aged with the worm1-1.

rl`he switch members 20 and 21, which are operated respectivelyv by theadjustable cams 18 and 19, are pivotally mounted upon suitable supportsSO extending` from the insulated base 31. Fach of the movable switchmembers carries a roller 32 'for engaging with the corresponding`operating` cam. lt. will be evident that the amount of rotation of theoperating,` shaft 12 required to etliect operation ot the switch member20 is dependent upon the angular position ot the cam element 1S on thegear wheel 15. rFhus, by adjusting the cam element 1S so to engage theloclzine' pins L3 with each ot the series ot lockingr holes 'formed inthe gear wheel 15. operation ot the switch member 2O may be effectedover a wide range ot rotation of the operating shatt- 12 1n addition tothe wide range adjustment provided by adjusting' the angular 'positioncam element on the gear wheel, a fine control ot the operation ot theswitch member 20 is obtained by varying the position of the roller 32 inthe path ot the operating cam 18. lt will be observed that thestationary contact 38, cooperating' with the movable switch member 20,is screw-threaded into the support 3l and hence is adjustable. Thus byscrewing' or unscrewing the stationary contact 33 the contact 2O israised or lowered to thereby vary the position of the roller 32 in the'path of cam 18. The combination of the rough adjustment and the lineadjustment permits the greatest accu acv to be obtained in the operationet the swi ch member over a very wide range ot operation of the shaft12.

rilhe operation of the switch member 21 is etlected by the cam element19 which may occupy any desired angular position with refinn a Jonghadjutment may be obtained by reniox'inf" the gear wheel 15 'from theshalt 16 )reviously described.

rEhen the degree ot it 12 retfbuired to elicct operach member 21 may beadj usted "arising or lowering` the member 21. Th is ing the positiono'l' the scribes'. imit .switch mechanism is row-closing; service thevery ac nice adjustment permits the coniV ned just as the window isoilieriited ll closed position. ln such service t .i i member 21employed to interrupt the motor circuit when the vindow ha s i i tueopen position where a hi f accuracyv is not required. f urne number orwindm'fs `green house. or otl similar build-v r ie adjustim itspermitted b v the limit justdescribod overcomes the diiiculf i toiations in the amount of openhercnt windoi'v.1 as well as inare to beone 'ated L the di in mounting or connecting the limit i therewith.order to acilitat circuits t be contro`l l bv the limit switchmerhanisri the termi; als ffl and Si 'for switch 21 are mounted on theside o` base 31 as the i i l 'itch 20.

i., n. i nected to th evident t iat adjustmeut,r the accuraci ofopg'ether with the wide ra j e of adas well as the simple and econstruction of the several oiierative pa. render the swi'ch su: abletor a wide field ot serv'ce and particular .y adapted i'or the controlof electrically operated windows.

lhat l claim as new and de]` e to secure by Leters Patent of the UnitedStates is 1. A switch mechanism comprising' a movable switch member, acam elen for ope-r` ating the switch member, a rotatable member w 4.Qllu having means for supporting the cam element thereon to ermit bothaxial and angular movement ci) the cam element with respect to therotatable member, and axially detachable interlocking elements on thecam member and the rotatable member for connecting the same together forrotation in unison in each of a plurality of angular relations.

2. The combination of a movable switch member, a cam operating mechanismtherefor comprising a rotatably mounted gear wheel having a series ofholes radially disposed thereon, a cam member mounted on the hub of thegear wheel to permit both axial and rotational movement of the cammember with respect to the gear wheel, a locking pin carried by the cammember and adapted to engage with any selected one of the series ofholes in the gear wheel, and a spring mounted on the hub of the gearwheel for resiliently holding the cam in locked engagement with the gearwheel.

3. A switch mechanism including relatively movable switch members, arotatable member, a cam element adjustablv mounted upon the rotatablemember for effecting relative movement between the switch members uponangular movement of the rotatable member, and a member adjustablydisposed in the path of the cam element and cooperating therewith forvarying the angular movement of the rotatable member required to effectrelative movement between the switch members.

l. The combination of a movable switch operating member, a rotatableoperating cam therefor, a rotatable member concentrically mounted withrespect to said cam element, means for locking the cam element to thesaid rotatable element in each of a series of definite angularpositions, and means for varying the position of the said switchoperating member in the path of the cam element for varying the angularmovement of said rotatable member required to effect movement of theswitch operating member with the cam element in each of said angularpositions.

5. The combination of a rotatable member having a cam member rotatablysupported thereon, one of said members having a series of locking holesformed therein and the other of said members having a locking pinadapted to be received in any selected one of said holes, means forresiliently holding said members in locked engagement, a switch havingan operating member disposed in the path of movement of said cam memberto be operated thereby, and means for adjusting the position of saidoperating member in the path of said cam member to vary the angularmovement of said rotatable member required to effect operation of theswitch.

6. The combination with a pair of movable switch members of an operatingmechanism therefor comprising a rotatable gear wheel having an operatingcam on each side thereof for operating a corresponding one of the switchmembers, said operating cams being angularly adjustable with respect toeach other.

7. The combination of relatively movable circuit controlling contacts, arotatable member having acam element angularly adjustable thereon, amember disposed in the path of movement of the said cam element to beope ated thereby upon rotation of said rotatable member an amountdependent upon the angular adjustment of said cam element thereon, saidmember being connected to effect relative movement of said contacts, andmeans for adjusting the position of said member with respect to the pathof movement of the said cam element.

8. A limit switch mechanism comprising an enclosing casing having a pairof movable switch members mounten in spaced relation therein, a gearwheel mounted in the casing for rotation in a plane between said switchmembers, a worm gear in mesh with said gear wheel and having a shaftextending through said casing, a pair of cam elements mounted onopposite sides of said gear wheel each in operative relation with acorresponding one of said switch members, the position of each of saidcams being adjustable to vary the rotational movement of said worm gearrequired to effect operation of the corresponding switch member.

9. A limit switch mechanism comprising a casing having an operatingshaft rotatably mounted in one side thereof, a worm gear secured to theend of the shaft within said casing, a gear wheel removably mounted inmesh with said worm gear, a cam element fixedly secured to one side ofsaid gear wheel, a second cam element adjustably mounted on the otherside of said gear wheel and adjustable into each of a series of definiteangular positions thereon, and a pair of movable circuit controllingcontacts each mounted in spaced relation with a corresponding one ofsaid cam elements to be operated thereby upon a predetermined operationof said operating shaft.

In witness whereof, I have hereunto set my hand this 17th day ofJanuary, 1928.`

LEONARD P. HUTT.

